U.S. Pat. No. 3,784,489 discloses an ion exchange resin which is the condensation product of a dihaloalkane with a polyethylene amine. Thereafter, this patent discloses methylating the non-tertiary amine groups of the condensation product to convert these groups of tertiary or quaternary amines. The patent also discloses that the polyethylene amine used must be one which has a molecular weight of from 300 to 60,000. It is believed that this description concerning the molecular weight of the polyethylene amine, exists because, if the polyamine has a molecular weight below 300, then the condensation product of the dihaloalkane and the polyethylene amine tends to be too soft and deformable for use as an ion exchange resin.
Another class of materials which may be used to prepare an ion exchange resin is the condensation product of the epihalohydrins with a polyamine. When an epihalohydrin-polyamine condensation product is used as an ion exchange resin, such an ion exchange resin has been found to suffer from a lack of oxidative stability which severely limits the use of such resin in commercial ion exchange applications.
It is generally believed that the presence of secondary hydroxyl groups on a polymer which is to be used as an ion exchange resin renders the ion exchange resin susceptible to oxidative instability during normal use and results in subsequent poor performance of the resin. Therefore, the presence of secondary hydroxyl groups on a polymer used as an ion exchange resin has usually been provided.
Oxidative instability results in a physical breakdown of the resin particles during use, so that such resin particles will commonly shatter when used as normally intended. In addition, such oxidative instability results in a resin which requires excessive amounts of regenerating material to regenerate the column due to the fact that the oxidized resins have reduced ion exchange properties.
In accordance with the present invention, it has now been found that when an epihalohydrin is reacted with a polyamine, which polyamine has a molecular weight of from about 60 to about 298, and thereafter the primary or secondary amine groups are alkylated to convert such groups to tertiary or quaternary amines, the resultant alkylated polymer is not only satisfactory for use as an ion exchange resin, but exhibits enhanced oxidative stability beyond that which would be normally expected.
Because the alkylated polymers of this invention all contain secondary hydroxyl groups, it was surprising to find that ion exchange resins comprising such polymers were not oxidatively unstable but actually exhibited enhanced oxidative stability.
It is an object of this invention, therefore, to provide an ion exchange resin having good oxidative stability from an epihalohydrin-polyamine condensation product.
A further object of this invention is to produce such a resin from a polyamine having a molecular weight of from about 60 to about 298.
A still further object of this invention is to provide a process for producing an ion exchange resin which has good oxidative stability.
Other objects and advantages will become apparent from the following more complete description and claims.